This invention relates to control systems and, more particularly, to a user friendly input device for issuing commands to a control system.
By and large, push buttons are binary in nature, i.e., ON or OFF. When employed as an input device to issue commands to a control system, a binary push button offers the user only one variable, namely the ON time. When the push button is depressed, an analog or digital signal having constant characteristics is applied as the command to the control system.
U.S. Pat. No. 3,643,418, which issued on Feb. 22, 1972 to H. S. Polin, et al., discloses a time-setting device for an electronic watch in which a spring biased push button produces a signal having a characteristic representative of applied force. Thus, there are two variables that contribute to the command--namely, force and time. The push button of Polin, et al., controls the frequency of an oscillator such that the greater the applied force, the smaller is the frequency. The oscillator output is coupled to a counting device to count unidirectionally the pulses generated by the oscillator.
U.S. Pat. No. 3,843,873 which issued Oct. 22, 1974 to R. E. Beville, et al., discloses a counter having selective direction and a voltage to frequency convertor that feeds the counter variable rate control. The count of the counter is set by a rotatable spring biased control knob. A voltage is generated proportional to the torque applied to the control knob. This voltage is converted to pulses of related frequency which are applied to the counter. When the control knob is turned in one direction, the counter is incremented; in the other direction, the counter is decremented.